How can Hand Mixing of Concrete be Performed?

It is very interesting to know that a set of bad ingredient cannot produce a good concrete but a set of good ingredient cannot ensure a good concrete if intensive care is not taken. So to produce a good concrete it is required to know the good practice of concreting following the standard rules. Each stage of concreting process is important. Of the various stages of concreting, mixing, particularly hand mixing is discussed here.

To manufacture a concrete of uniform strength and durability properties, it should have uniformity. This uniformity is ensured by proper mixing of concrete. Mixing ensure a concrete mass of uniform color, consistency that produce a homogeneous mass of concrete. Mixing can be performed by two methods:

1. Hand mixing

2. Machine mixing
Impervious brick or concrete floor is required as platform to mix all ingredients of concrete. The platform should be large enough to mix a concrete mix of one bag cement. At first according to the mix ratio the quantity of the coarse aggregate and fine aggregate are calculated. These two types of aggregate are spread in alternate layers. The cement are poured on top of them and in dry condition they are mixed by shovel. The mixture is turned over repeatedly to achieve a mixture of uniform color. When color becomes uniform, the mixer is spread in a thickness of around 200 cm. Now a water can having arrangement of sprinkling like rose-head are used to sprinkling the water. It should be noticed that water should be sprinkled not poured to avoid washout of green cement water. With sprinkling of water the turning over process is continued till a homogeneous and uniform concrete is found. It should be noticed that amount of water is determined from water/cement ratio as defined in mix design. Of this amount of water small amount of water is left not used. The rest water is added at the ending of mixing to just reach the required workability.
The most important things that I have forgotten to discuss is the feasibility of hand mixing. Hand mixing is exercised in small and less important concreting work. This is due to the probability of having inefficient and not uniform mix. A 10% excess cement is used sometimes to avoid inferior concrete that are supposed to produce by this method.